1. Field of the Invention
The present invention relates to data communication apparatus and method and, more particularly to data communication apparatus and method which performs data communication such that the communication protocol for data communication between a host device and a target device is not limited on the target device.
Further, the present invention relates to a data Communication apparatus and method in a network where devices having a plurality of protocols are connected via a serial bus.
2. Description of Related Art
Various types of systems which transfer data to a printer via a bus are known. For example, a known technique is to output data from a computer to the printer by using a defacto standard interface such as a SCSI (Small Computer System Interface) or Centronics interface.
However, printer manufacturers respectively provide a printer protocol unique to their printer for transferring data to the printer via these interfaces, thus lacking versatility.
Particularly, upon outputting print data by using a serial interface connecting various types of devices, such as an IEEE 1394 interface, it is desirable to solve the above problem of the lack of versatility.
The present invention has its object to provide data communication apparatus and method which enable data communication such that the communication protocol between a host device and a target device is not limited on the target device.
Further, another object of the present invention is to provide data communication apparatus and method appropriate to data communication using a serial interface based on, e.g., the IEEE 1394 standards.
Further, another object of the present invention is to provide data communication apparatus and method appropriate to directly transfer image data from a host device to a target device without a host computer.
According to the present invention, the forging objection are attained by providing a communication system comprising a first device, a second device, and a serial bus which defines a predetermined address space for each of the first and second devices, wherein the first device includes first protocol capability storage means, which is in the address space defined by the serial bus, for storing information on usability of respective data transport protocols, the second device includes: first identifying means for reading contents of the first protocol capability storage means by designating an address defined by the serial bus and identifying the read contents; and first determination means for determining a data transport protocol on the basis of the contents of the first protocol capability storage means, wherein the first identifying means identifies a plurality of usable data transport protocols in advance of determination by the first determination means.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, characterized by comprising the steps of: obtaining capability information of a target device by communication using an initial protocol; having the target device set a communication protocol which can be used in data communication, based on the obtained capability information; and performing the data communication with the target device based on the set communication protocol.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, characterized by comprising the steps of: returning capability information to a host device in response to a request using an initial protocol from the host device; setting a communication protocol to be used in data communication, in accordance with an instruction from the host device based on the capability information; and performing data communication with the host device based on the set communication protocol.
Further, the foregoing objects are attained by providing a data communication apparatus for performing data communication on a serial bus, characterized by comprising: communication means corresponding to an initial protocol and a plurality of communication protocols for data communication; storage means in which capability information including information indicative of the plurality of communication protocols is stored; and setting means for setting a communication protocol of the communication means, wherein the communication means sends the capability information stored in the storage means based on a request by using the initial protocol from a host device, and the setting means sets the communication protocol of the communication means in accordance with an instruction by using the initial protocol from the host device.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, characterized by comprising the steps of: receiving a connection request from a host device; setting the communication protocol to be used in data communication if it is recognized that the host device does not correspond to a predetermined protocol; trying communication with the host device by the set communication protocol; and performing the data communication with the host device by using the set communication protocol, if the communication with the host device is established.
Further, the foregoing objects are attained by providing a data communication apparatus for performing data communication on a serial bus, characterized by comprising: communication means corresponding to an initial protocol and a plurality of communication protocols for data communication; and control means for controlling the data communication with a host device, wherein if the control means recognizes, from a connection request received by the communication means from the host device, that the host device does not correspond to the initial protocol, the control means sets a predetermined communication protocol at the communication means, tries communication with the host device by the set communication protocol, and if the communication with the host device is established, performs data communication with the host device by using the set communication protocol.
Further, another object of the present invention is to provide a data communication apparatus and method which adjust the protocol for a host device which does not correspond to an initial protocol.
According to the present invention, the foregoing object is attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: obtaining an identifier of a host device which does not correspond to an initial protocol; recognizing a protocol of the host device based on the obtained identifier; and setting the protocol as a communication protocol for communication with the host device, if the recognized protocol is available.
Further, another object of the present invention is to provide a data communication apparatus and method which reduce the frequency of protocol change in a multi-protocol environment, to prevent degradation of efficiency due to protocol re-setting.
According to the present invention, the foregoing object is attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: obtaining capabilities of devices connected to the serial bus; counting protocols of the devices, by each type, based on the obtained capabilities; determining one of the protocols to be used with priority, based on the result of counting; and notifying the determined protocol to the devices.
Further, the foregoing object is attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: executing an initial protocol; and if a protocol to be executed after the initial protocol is selected from plural types of protocols, selecting a specific protocol with priority.
Further, another object of the present invention is to provide a data communication apparatus and method which, in a network to which a plurality of target devices are connected, select a target device corresponding to an output purpose, to obtain appropriate output.
Further, another object of the present invention is to provide a data communication apparatus and method which reduce load due to protocol change in a multi-protocol environment.
According to the present invention, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: searching for target devices connected to the serial bus; obtaining information on the target devices; generating a table of the target devices based on the obtained information; and selecting one of the target devices based on the generated table.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: searching for target devices connected to the serial bus; obtaining information on the target devices; recognizing a network topology based on the obtained information; and selecting one of the target devices based on the recognized network topology.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: searching for target devices connected to the serial bus; obtaining information on the target devices; generating a table of the target devices based on the obtained information; and selecting one of the target devices based on the generated table.
Further, the foregoing objects are attained by providing a data communication method for performing data communication on a serial bus, comprising the steps of: searching for target devices connected to the serial bus; obtaining information on the target devices; generating a table of the target devices based on the obtained information; determining a protocol to be used with priority, based on the generated table; and notifying the target devices connected to the serial bus of the determined protocol.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same name or similar parts throughout the figures thereof.